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Recent & Highlighted Publications & Presentations

Photochemistry

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Photochemistry/Photophysics
Bioinorganic Chemistry of SMBs
Sustainable Chemistry & Biomass Conversion

Presentations by subject

Biomass/Sustainable Chemistry
Photochemistry/Small Molecule Bioregulators

Photochemistry/Photophysics Papers

Dinuclear PhotoCORMs: Dioxygen-Assisted Carbon Monoxide Uncaging from Long-Wavelength-Absorbing Metal–Metal-Bonded Carbonyl Complexes

Li, Z.; Pierri, A. E.; Huang, P.-J.; Wu, G.; Iretskii, A. V.; Ford, P. C. Inorganic Chemistry 2017

DOI: 10.1021/acs.inorgchem.6b03138

Abstract

We describe a new strategy for triggering the photochemical release of caged carbon monoxide (CO) in aerobic media using long-wavelength visible and near-infrared (NIR) light. The dinuclear rhenium–manganese carbonyl complexes (CO)5ReMn(CO)3(L), where L = phenanthroline (1), bipyridine (2), biquinoline (3), or phenanthrolinecarboxaldehyde (4), each show a strong metal–metal-bond-to-ligand (σMM → πL*) charge-transfer absorption band at longer wavelengths. Photolysis with deep-red (1 and 2) or NIR (3 and 4) light leads to homolytic cleavage of the Re–Mn bonds to give mononuclear metal radicals. In the absence of trapping agents, these radicals primarily recombine to reform dinuclear complexes. In oxygenated media, however, the radicals react with dioxygen to form species much more labile toward CO release via secondary thermal and/or photochemical reactions. Conjugation of 4, with an amine-terminated poly(ethylene glycol) oligomer, gives a water-soluble derivative with similar photochemistry. In this context, we discuss the potential applications of these dinuclear complexes as visible/NIR-light-photoactivated CO-releasing moieties (photoCORMs).


A photoCORM nanocarrier for CO release using NIR light

Feb 2015

Pierri AE, Huang PJ, Garcia JV, Stanfill JG, Chui M, Wu G, Zheng N, & Ford PC. Chemical Communications 2015, 51, 2072-5. 

DOI: 10.1039/C4CC06766E

NIR sensitive photoCORM in nanocarrier

Abstract

A water-soluble nanocarrier for a photo-activated CO releasing moiety (photoCORM) that can be triggered with NIR excitation is described.  This has an upconversion nanoparticle core encapsulated by an amphiphilic polymer imparting both water solubility and a hydrophobic interior containing the photoCORM trans-Mn(bpy)(PPh3)2(CO)2. Such an ensemble offers a unique strategy for CO delivery to biol. targets.


Synthesis and Properties of Phosphine-Substituted Ruthenium(II) Polypyridine Complexes with Nitrogen Oxide

4. August 2015

Nakamura G, Kondo M, Crisalli M, Lee SK, Shibata A, Ford PC, & Masaoka S. Dalton Transactions, 2015, in press. 

DOI: 10.1039/C5DT02994E

Abstract

Four novel phosphine-substituted ruthenium(II) polypyridine complexes with nitrogen oxides—trans(P,NO2)-[Ru(trpy)(Pqn)(NO2)]PF6 (trans-NO2), cis(P,NO2)-[Ru(trpy)(Pqn)(NO2)]PF6 (cis-NO2), [Ru(trpy)(dppbz)(NO2)]PF6 (PP-NO2), and cis(P,NO)-[Ru(trpy)(Pqn)(NO)](PF6)3 (cis-NO)—were synthesised (trpy = 2,2’:6’,2”-terpyridine, Pqn = 8-(diphenylphosphanyl)quinoline, and dppbz = 1,2-bis(diphenylphosphanyl)benzene). The influence of the number and position of the phosphine group(s) on the electronic structure of these complexes was investigated using single-crystal X-ray structural analysis, UV-vis absorption spectroscopy, and electrochemical measurements. The substitution lability of the nitrogen oxide ligand of each complex is discussed in comparison with that of the corresponding acetonitrile complexes.


Photoreactivity of a Quantum Dot-Ruthenium Nitrosyl Conjugate

18. Nov 2014 

Franco LP, Cincillini SA, Biazzotto JC, Schiavon MA, Mikhailovsky A, Burks PT, Garcia JV, Ford PC, & Silva RS. Journal of Physical Chemistry A2014118, 12184-12191. 

DOI: 10.1021/jp5111218

Abstract

Photoreactivity of QD-Ru-NO conjugateWe describe the use of cadmium telluride quantum dots (CdTe QDs) as antennas for the photosensitization of nitric oxide release from a ruthenium nitrosyl complex with visible light excitation.  The CdTe QDs were capped with mercaptopropionic acid to make them water-sol., and the ruthenium nitrosyl complex was cis-[Ru(NO)(4-ampy)(bpy)2]3+ (Ru-?NO; bpy is 2,2'-?bipyridine, and 4-ampy is 4-aminopyridine).  Solns. of these two components demonstrated concn.-dependent quenching of the QD photoluminescence (PL) as well as photoinduced release of NO from Ru-NO when irradiated by 530 nm light.  A NO release enhancement of ∼8 times resulting from this assocn. was obsd. under longer wavelength excitation in visible light range.  The dynamics of the quenching detd. by both PL and transient absorption measurements were probed by ultrafast flash photolysis.  A charge transfer mechanism is proposed to explain the quenching of the QD excited states as well as the photosensitized release of NO from Ru-NO.


Photo-controlled release of NO and CO with inorganic and organometallic complexes. 

Mar 2015 

Pierri AE, Muizzi DA, Ostrowski AD, & Ford PC. Structure and Bonding2015, 165, 1-45. 

DOI: 10.1007/430_2014_164

Abstract

The photochemical delivery of bioactive small molecules to physiological targets provides the opportunity to control the location, timing, and dosage of such delivery. We will discuss recent developments of the synthesis and studies of various metal complexes designed for targeted release of the bioregulatory diatomics nitric oxide and carbon monoxide. Of considerable interest are those systems where the NO or CO precursor and/or the photochemical product is luminescent such that imaging techniques allow one to identify the release location.


Photocatalytic Carbon Disulfide Production via Charge Transfer Quenching of Quantum Dots

12. Feb 2014 - JACS Cover

Bernt, CM; Burks, PT; DeMartino, AW; Pierri, AE; Levy, ES; Zigler, DF; Ford, PC.  J. Am. Chem. Soc2014, 136(6), 2192-2195. 

DOI: 10.1021/ja4083599

Artistic interpretation of DTO cleavage on QD surfacesAbstract

Carbon disulfide, a potentially therapeutic small molecule, is generated via oxidative cleavage of 1,1-dithiooxalate (DTO) photosensitized by CdSe quantum dots (QDs). Irradiation of DTO–QD conjugates leads to λirr independent photooxidation with a quantum yield of ~4% in aerated pH 9 buffersolution that drops sharply in deaerated solution. Excess DTO is similarly decomposed, indicating labile exchange at the QD surfaces and a photocatalyticcycle. Analogous photoreaction occurs with the O-tert-butyl ester tBuDTO in nonaqueous media. We propose that oxidation is initiated by hole transfer from photoexcited QD to surface DTO and that these substrates are a promising class of photocleavable ligands for modifying QD surface coordination

Light induced DTO cleavage on QD suffices.  Results in luminescence recovery (orange) as CS2 and CO2 are released.

 

 

 

 

 

A video explaining the details of this intriguing process can be found in our photochemistry section, here.  

This paper is also featured in Spotlights of Recent JACS PublicationsJ. Am. Chem. Soc2014, 136(6), 2177, found here.  

UPDATE 2/18/14: This paper is featured as a podcast on JACS Beta, you can hear the interview with Tony DeMartino here, podcast # 48. 


Nitric Oxide Releasing Materials Triggered by Near-Infrared Excitation through Tissue Filters

18. Nov 2013

Burks, PT; Garcia, JV; GonzalezIrias, R; Tillman, JT; Niu, M; Mikhailovsky, AA; Zhang, J; Zhang, F; Ford, PC.  J. Am. Chem. Soc. 2013, Just accepted.  

DOI: 10.1021/ja408516w

Abstract
NO release stimulated by near-IR light through tissue. Novel materials for the photo-therapeutic release of the bioregulator nitric oxide (nitrogen monoxide) are described. Also reported is a method for scanning these materials with a focused NIR beam to induce photo-uncaging while minimizing damage from local heating. The new materials consist of poly(dimethylsiloxane) composites with near infrared-to-visible upconverting nanoparticles (UCNPs) that are cast into a biocompatible polymer disk (PD). These PDs are then impregnated with the photochemical nitric oxide precursor Roussin's black salt (RBS) to give UCNP_RBS_PD devices that generate NO when irradiated with 980 nm light. When the UCNP_RBS_PD composites were irradiated with NIR light through filters composed of porcine tissue, physiologically relevant NO concentrations were released, thus demonstrating the potential of such devices for minimally-invasive photo-therapeutic applications.


Multi-Photon Excitation in Uncaging the Small Molecule Bioregulator Nitric Oxide

17. Jun 2013

Garcia JV, Zhang F, & Ford PC. Philosophical Transactions of the Royal Society, A: Mathematical, Physical & Engineering Sciences, 2013, 371, 20120129 - . 

DOI: 10.1098/rsta.2012.0129

Abstract

Multi-photon excitation allows one to use tissue transmitting near-infrared (NIR) light to access excited states with energies corresponding to single-photon excitation in the visible or ultraviolet wavelength ranges. Here, we present an overview of the application of both simultaneous and sequential multi-photon excitation in studies directed towards the photochemical delivery (‘uncaging’) of bioactive small molecules such as nitric oxide (NO) to physiological targets. Particular focus will be directed towards the use of dyes with high two-photon absorption cross sections and lanthanide ion-doped upconverting nanoparticles as sensitizers to facilitate the uncaging of NO using NIR excitation.


NIR-Triggered Release of Caged Nitric Oxide using Upconverting Nanostructured Materials

21. Dec 2012 - Small Cover

Our Small cover

Garcia, JV; Yang, JP; Shen, DK; Yao, C; Li, XM; Wang, R; Stucky, GD; Zhao, DY; Ford PC; Zhang, F.  Small.  2012, 8, 24, 3800-3805.
DOI: 10.1002/smll.201201213

Abstract
In this manuscript, a novel strategy for the therapeutic delivery of nitric oxide to physiological targets is described.  Nitric oxide (NO) is a key vasodilator in mammalian cardiovascular systems and has been shown to sensitize tissue to gamma-radiation. However, photochemical NO precursors that can be activated by these near-infrared (NIR) wavelengths are extremely limited. Herein, we have addressed this issue by utilizing the known NIR to visible upconversion properties of lanthanide cations doped NaYF4 nanocrystals. This result is a potential game changer in multiphoton excitation based therapeutic delivery of NO and other small molecule bioregulators.


 

Bioinorganic Chemistry of Small Molecule Bioregulators (SMBs) Papers

Dinitrosyl Iron Complexes with Cysteine. Kinetics Studies of the Formation and Reactions of DNICs in Aqueous Solution

5. Dec 2014

Pereira JCM, Iretskii AV, Han RM, & Ford, PC. J. Am. Chem. Soc. 2015137, 328-336. 

DOI: 10.1021/ja510393q

Abstract

Kinetics of DNICs

Kinetics studies provide mechanistic insight regarding the formation of dinitrosyl iron complexes (DNICs), which are now viewed as playing important roles in the mammalian chem. biol. of the ubiquitous bioregulator nitric oxide (NO).  Reactions in deaerated aq. solns. containing FeSO4, cysteine (CysSH), and NO demonstrate that both the rates and the outcomes are markedly pH dependent.  The dinuclear DNIC Fe2(u-CysS)2(NO)4, a Roussin's red salt ester (Cys-RSE), is formed at pH 5.0 as well as at lower concns. of cysteine in neutral pH solns.  The mononuclear DNIC Fe(NO)2(CysS)2- (Cys-DNIC) is produced from the same three components at pH 10.0 and at higher cysteine concentrations at neutral pH.  The kinetics studies suggest that both Cys-RSE and Cys-DNIC are formed via a common intermediate Fe(NO)(CysS)2-. Cys-DNIC and Cys-RSE interconvert, and the rates of this process depend on the cysteine concn. and on the pH.  Flash photolysis of the Cys-RSE formed from Fe(II)/NO/cysteine mixts. in anaerobic pH 5.0 soln. led to reversible NO dissocn. and a rapid, second-?order back reaction with a rate const. kNO = 6.9 × 107 M-1 s-1.  In contrast, photolysis of the mononuclear-DNIC species Cys-DNIC formed from Fe(II)/NO/cysteine mixts. in anaerobic pH 10.0 soln. did not labilize NO but instead apparently led to release of the CysS radical.  These studies illustrate the complicated reaction dynamics interconnecting the DNIC species and offer a mechanistic model for the key steps leading to these non-heme iron nitrosyl complexes.


Six-coordinate Nitrito and Nitrato Complexes of Manganese Porphyrin

4. Nov 2014

Kurtikyan TS, Hayrapetyan VA, Mehrabyan MM, & Ford PC. Inorganic Chemistry201453, 11948-11959. 

DOI: 10.1021/ic5014329

AbstractNitrite and nitrate complexes of manganese porphyrin

Reaction of small increments of NO2 gas with sublimed amorphous layers of MnII(TPP) (TPP = meso-tetra-phenylporphyrinato dianion) in a vacuum cryostat leads to formation of the 5-coordinate monodentate nitrato complex MnIII(TPP)(1-ONO2) (II). This transformation proceeds through the two distinct steps with initial formation of the five coordinate O-nitrito complex MnIII(TPP)(1-ONO) (I) as demonstrated by the electronic absorption spectra and by FTIR spectra using differently labeled nitrogen dioxide. A plausible mechanism for the second stage of reaction is offered based on the spectral changes observed upon subsequent interaction of 15NO2 and NO2 with the layered Mn(TPP). Low-temperature interaction of I and IIwith the vapors of various ligands L (L = O-, S-, and N-donors) leads to formation of the 6-coordinate O-nitrito MnIII(TPP)(L)(1-ONO) and monodentate nitrato MnIII(TPP)(L)(1-ONO2) complexes, respectively. Formation of the 6-coordinate O-nitrito complex is accompanied by the shifts of the (NO) band to lower frequency and of the (N–O) band to higher frequency. The frequency difference between these bands ?? = (NO) – (N–O) is a function of L and is smaller for the stronger bases. Reaction of excess NH3 with I leads to formation of Mn(TPP)(NH3)(?1-ONO) and of the cation [Mn(TPP)(NH3)2]+ plus ionic nitrite. The nitrito complexes are relatively unstable, but several of the nitrato species can be observed in the solid state at room temperature. For example, the tetrahydrofuran complex Mn(TPP)(THF)(1-ONO2) is stable in the presence of THF vapors (∼5 mm), but it loses this ligand upon high vacuum pumping at RT. When L = dimethylsulfide (DMS), the nitrato complex is stable only to ~−30 °C. Reactions of II with the N-donor ligands NH3, pyridine, or 1-methylimidazole are more complex. With these ligands, the nitrato complexes MnIII(TPP)(L)(1-ONO2) and the cationic complexes [Mn(TPP)(L)2]+ coexist in the layer at room temperature, the latter formed as a result of NO3–displacement when L is in excess.


Reaction of a Bridge Frustrated Lewis Pair with Nitric Oxide: A Kinetics Study

5. Jan 2014

Pereira, JCM; Sajid, M; Kehr, G; Wright, AM; Schirmer, B; Qu, ZW; Grimme, S; Erker, G; Ford, PC. J. Am. Chem Soc2014, 136(1), 513-519. 

DOI: 10.1021/ja4118335

Abstract
Frustrated Lewis pair (FLP) reaction with nitric oxideDescribed is a kinetics and computational study of the reaction of NO with the intramolecular bridged P/B frustrated Lewis pair (FLP) endo-2-(dimesitylphosphino)-exo-3-bis(pentafluorophenyl)boryl-norbornane to give a persistent FLP-NO aminoxyl radical. This reaction follows a second-order rate law, first-order in [FLP] and first-order in [NO], and is markedly faster in toluene than in dichloromethane. By contrast, the NO oxidation of the phosphine base 2-(dimesitylphosphino)norbornene to the corresponding phosphine oxide follows a third-order rate law, first-order in [phosphine] and second-order in [NO]. Formation of the FLP-NO radical in toluene occurs with a ?H of 13 kcal mol–1, a feature that conflicts with the computation-based conclusion that NO addition to a properly oriented B/P pair should be nearly barrierless. Since the calculations show the B/P pair in the most stable solution structure of this FLP to have an unfavorable orientation for concerted reaction, the observed barrier is rationalized in terms of the reversible formation of a [B]-NO complex intermediate followed by a slower isomerization–ring closure step to the cyclic aminoxyl radical. This combined kinetics/theoretical study for the first time provides insight into mechanistic details for the activation of a diatomic molecule by a prototypical FLP.


Nitrite reduction mediated by heme models. Routes to NO and HNO? 

19. Feb 2013

Heinecke JL, Khin C, Pereira JCM, Suárez SA, Iretskii AV, Doctorovich F, & Ford PC. J. Am. Chem. Soc. 2013135, 4007-4017. 

DOI: 10.1021/ja312092x

Abstractproduction of NO and HNO?

The water-soluble ferriheme model FeIII(TPPS) mediates oxygen atom transfer from inorganic nitrite to a water soluble phosphine (tppts), dimethyl sulfide, and the biological thiols cysteine (CysSH) and glutathione (GSH). The products with the latter reductant are the respective sulfenic acids CysS(O)H and GS(O)H, although these reactive intermediates are rapidly trapped by reaction with excess thiol.  The nitrosyl complex FeII(TPPS)(NO) is the dominant iron species while excess substrate is present.  However, in slightly acidic media (pH ~6), the system does not terminate at this very stable ferrous nitrosyl.  Instead it displays a matrix of redox transformations linking spontaneous regeneration of FeIII(TPPS) to the formation of both N2O and NO. Electrochemical sensor and trapping experiments demonstrate that HNO (nitroxyl) is formed, at least when tppts is the reductant.  HNO is the likely predecessor of the N2O. A key pathway to NO formation is nitrite reduction by FeII(TPPS), and the kinetics of this iron-mediated transformation are described.  Given that inorganic nitrite has protective roles during ischemia/reperfusion (I/R) injury to organs, attributed in part to NO formation, and that HNO may also reduce net damage from I/R, the present studies are relevant to potential mechanisms of such nitrite protection.


New Zn(II) complexes with N2S2 Schiff Base Ligands. Experimental and Theoretical Studies of the Role of Zn(II) in Disulfide-Thiolate Exchange. 

29. Mar 2014

Amirnasr M, Bagheri M, Farrokhpour H, Schenk KJ, Mereiter K, & Ford PC. 2014136, 513-519. 

DOI: 10.1021/ja4118335

Zn(II) complexes with N2S2 Schiff base ligandsAbstract

Described are the synthesis and characterization of two, potentially tetradentate, N2S2 Schiff-base ligands, containing a disulfide bond, N,N′-bis(3-phenylprop-2-en-1-ylidene)-2,2′-disulfanediyldianiline (L1) and N,N′-bis(3,3-diphenylprop-2-en-1-ylidene)-2,2′-disulfanediyldianiline (L2), and their reaction with Zn2+. Surprisingly, both L1 and L2 undergo reductive disulfide bond scission upon reaction with Zn2+ in alcoholic media to give, under alcohol oxidation, the respective Zn(NS)2 complexes Zn(L3)2 (1) and Zn(L4)2 (2), where the Land Lare the respective bidentate thiolate-imine anions. The ligands L1 and L2 and the complexes 1 and 2 have been characterized spectroscopically, and the crystal and molecular structures of the two complexes have been determined by single crystal X-ray diffraction. The coordination geometry around Zn(II) centers in both complexes is a distorted tetrahedron. In addition, DFT calculations (B3LYP/LANL2DZ/6-311++G(d,p)) support the structure of 1. Cyclic voltammetric studies demonstrate that Zn(II) shifts the reduction potential of the disulfide ligands L1 and L2 to less negative values thus making them more susceptible to reductive cleavage of the disulfide bond. The results of semi-empirical PM6 calculations offer key insight into the nature of the transition state for this reaction.


Tracking Reactive Intermediates by FTIR Monitoring of Reactions in Low-Temperature Sublimed Solids. Nitric Oxide Disproportionation Mediated by the Ruthenium(II) Carbonyl Porphyrin Ru(TPP)(CO)

13. Apr 2013 

Azizyan AS, Kurtikyan TS, Martirosyan GG, & Ford PC. Inorg. Chem. 201352, 5201-5205.

DOI: 10.1021/ic400102q

Ruthenium Carbonyl PorphyrinAbstract 

Interaction of NO (15NO) with amorphous layers of Ru(II) carbonyl porphyrin was monitored by FTIR spectroscopy from 80 K to room temperature. An intermediate spectrally characterized at very low temperatures (110 K) with ?(CO) at 2001 cm−1 and (NO) at 1810 (1777 cm−1 for 15NO isotopomer) was readily assigned to the mixed carbonyl−nitrosyl complex Ru(TPP)(CO)(NO), which is the logical precursor to CO labilization.


Weak coordination of neutral S- and O-donor proximal ligands to a ferrous porphyrin nitrosyl. Characterization of 6-Coordinate Complexes at Low T.

Apr 2013

Martirosyan GG, Kurtikyan TS, Hovhannisyan AA, Iretskii A, & Ford PC. J. Inorg. Biochem. 2013121, 129-133.

DOI:  10.1016/j.jinorgbio.2012.12.017

Abstract

The interaction of the S- and O-donor ligands tetrahydrothiophen (THT) and tetrahydrofuran (THF) with the ferrous nitrosyl complex Fe(TTP)(NO) (TTP2 − is meso-tetra-p-tolyl-porphyrinatodianion) was studied at various temperatures both in solid state and solution using electronic and infrared absorption spectroscopy. Upon addition of these ligands to a cryostat containing sublimed layers of Fe(TTP)(NO), no complex formation was detected at room temperature. However, upon lowering the temperature, spectral changes were observed that are consistent with ligand binding in axial position trans to the NO (the proximal site) and formation of the six-coordinate adducts. Analogous behavior was observed in solution. In both media, the six-coordinate adducts are stable only at low temperature and dissociate to the 5-coordinate nitrosyl complexes upon warming. 

Weak-coordination of of neutral S- and O-donor proximal ligands

The NO stretching frequencies of the six-coordinate thioether and ether complexes were recorded and binding constants for the weak bonding of proximal THF and THT ligands were determined from the spectral changes. These parameters are compared with those obtained for the N-donor ligand pyrrolidine.


Mechanisms of Nitric Oxide Reactions Mediated by Biologically Relevant Metal Centers 

5. Oct 2013

Ford PC, Pereira JCM, & Miranda KM. Structure and Bonding, 2013, book chapter. 

DOI: 10.1007/430_2013_117

Abstract

Here, we present an overview of mechanisms relevant to the formation and several key reactions of nitric oxide (nitrogen monoxide) complexes with biologically relevant metal centers. The focus will be largely on iron and copper complexes. We will discuss the applications of both thermal and photochemical methodologies for investigating such reactions quantitatively.


 

Sustainable Chemistry and Biomass Conversion Papers

 

Probing the Lignin Disassembly Pathways with Modified Catalysts Based on Cu-Doped Porous Metal Oxides

7 March 2017

Chui, M.; Metzker, G.; Bernt, C.M.; Tran, A.;Burtoloso A.C.; Ford, P.C.

DOI: 10.1021/acssuschemeng.6b02954

Abstract

Described are the selectivities observed for reactions of lignin model compounds with modifications of the copper-doped porous metal oxide (CuPMO) system previously shown to be a catalyst for lignin disassembly in supercritical methanol (Matson et al., J. Amer. Chem. Soc. 2011, 133, 14090–14097). The models studied are benzyl phenyl ether, 2-phenylethyl phenyl ether, diphenyl ether, biphenyl, and 2,3-dihydrobenzofuran, which are respective mimetics of the α-O-4, β-O-4, 4-O-5, 5-5, and β-5 linkages characteristic of lignin. Also, briefly investigated as a substrate is poplar organosolv lignin. The catalyst modifications included added samarium(III) (both homogeneous and heterogeneous) or formic acid. The highest activity for the hydrogenolysis of aryl ether linkages was noted for catalysts with Sm(III) incorporated into the solid matrix of the PMO structure. In contrast, simply adding Sm3+ salts to the solution suppressed the hydrogenolysis activity. Added formic acid suppressed aryl ether hydrogenolysis, presumably by neutralizing base sites on the PMO surface but at the same time improved the selectivity toward aromatic products. Acetic acid induced similar reactivity changes. While these materials were variously successful in catalyzing the hydrogenolysis of the different ethers, there was very little activity toward the cleavage of the 5-5 and β-5 C-C bonds that represent a small, but significant, percentage of the linkages between monolignol units in lignins.


Enhancing Aromatic Production from Reductive Lignin Disassembly: in situ O-methylation of Phenolic Intermediates.

Abstract Image15 Sept 2016

Barrett, J. A.; Gao, Y.; Bernt, C. M.; Chui, M.; Tran, A. T.; Foston, M. B.; Ford, P. C.

DOI: 10.1021/acssuschemeng.6b01827

Abstract

The selective conversion of lignin into aromatic compounds has the potential to serve as a “green” alternative to the production of petrochemical aromatics. Herein, we evaluate the addition of dimethyl carbonate (DMC) to a biomass conversion system that uses a Cu-doped porous metal oxide (Cu20PMO) catalyst in supercritical methanol (sc-MeOH) to disassemble lignin with little to no char formation. While Cu20PMO catalyzes C–O hydrogenolysis of aryl–ether bonds linking lignin monomers, it also catalyzes arene methylation and hydrogenation, leading to product proliferation. The MeOH/DMC co-solvent system significantly suppresses arene hydrogenation of the phenolic intermediates responsible for much of the undesirable product diversity via O-methylation of phenolic −OH groups to form more stable aryl-OCH3 species. Consequently, product proliferation was greatly reduced and aromatic yields greatly enhanced with lignin models, 2-methoxy-4-propylphenol, benzyl phenyl ether, and 2-phenoxy-1-phenylethan-1-ol. In addition, organosolv poplar lignin (OPL) was examined as a substrate in the MeOH/DMC co-solvent system. The products were characterized by nuclear magnetic resonance spectroscopy (31P, 13C, and 2D 1H–13C NMR) and gas chromatography–mass spectrometry techniques. The co-solvent system demonstrated enhanced yields of aromatic products.


Mapping reactivities of aromatic models with a lignin disassembly catalyst. Steps toward controlling product selecivity.

15 Nov 2015

Bernt, C. M., Bottari, G., Barrett, J. A., Scott, S. L., Barta, K., Ford P.C.

 

DOI: 10.1039/C5CY01555C

 

Abstract

Graphical abstract: Mapping reactivities of aromatic models with a lignin disassembly catalyst. Steps toward controlling product selectivityCopper-doped porous metal oxides catalyze the one-pot disassembly of biomass-derived lignin via C–O bond hydrogenolysis and hydrodeoxygenation in supercritical methanol. This catalytic system cleanly converts lignin as well as lignocellulose composites, such as sawdust, to organic liquids with little or no formation of intractable tars or chars. However, this catalyst based on Earth-abundant components also catalyzes less desirable aromatic ring hydrogenations and various methylations that contribute to the diversity of products. In this context, we undertook a quantitative experimental and computational evaluation of model reactions relevant to the reductive disassembly of lignin by this catalyst system in order to determine quantitatively the rates of desirable and less desirable chemical steps that define the overall product selectivities. Global fitting analysis methods were used to map the temporal evolution of key intermediates and products and to elucidate networks that provide guidelines regarding the eventual fates of reactive intermediates in this catalysis system. Phenolic compounds display multiple reaction pathways, but substrates such as benzene, toluene, and alkyl- and alkoxy-substituted aromatics are considerably more stable under these conditions. These results indicate that modifying this catalytic system in a way that controls and channels the reactivity of phenolic intermediates should improve selectivity toward producing valuable aromatic chemicals from biomass-derived lignin. To this end we demonstrate that the O-methylating agent dimethyl carbonate can intercept the phenol intermediate formed from hydrogenolysis of the model compound benzyl phenyl ether. Trapping the phenol as anisole thus gave much higher selectivity towards aromatic products.


Catalytic Conversion of Non-food Woody Biomass Solids to Organic Liquids

18. Apr 2014 

Barta K & Ford PC. Acc. Chem. Res. 201447, 1503-1512. 

DOI: 10.1021/ar4002894

Abstract

Conversion of Non-Food Woody Biomass solids to organic liquidsThis Account outlines recent efforts in our laboratories addressing a fundamental challenge of sustainability chemistry, the effective utilization of biomass for production of chemicals and fuels. Efficient methods for converting renewable biomass solids to chemicals and liquid fuels would reduce society's dependence on non-renewable petroleum resources while easing the atmospheric carbon dioxide burden. However, the major non-food component of biomass is lignocellulose, a matrix of the biopolymers cellulose, hemicellulose and lignin. New approaches are needed to effect facile conversion of lignocellulose solids to liquid fuels and to other chemical precursors without the formation of intractable side products and with sufficient specificity to give economically sustainable product streams.

We have devised a novel catalytic system whereby the renewable feedstocks cellulose, organosolv lignin and even lignocellulose composites such as sawdust are transformed into organic liquids. The reaction medium is supercritical methanol (sc-MeOH), while the catalyst is a copper-doped porous metal oxide (PMO) prepared from inexpensive, Earth-abundant, starting materials. This transformation occurs in a single stage reactor operating at 300-320 °C and 160-220 bar. The reducing equivalents for these transformations are derived by the reforming of MeOH (to H2 and CO), which thereby serves as a "liquid syngas" in the present case. Water generated by deoxygenation processes is quickly removed by the water gas shift reaction. The Cu-doped PMO serves multiple purposes, catalyzing substrate hydrogenolysis and hydrogenation as well as the methanol reforming and shift reactions. This one-pot “UCSB process” is quantitative, giving little or no biochar residual.

Provided is an overview of these catalysis studies beginning with reactions of the model compound dihydrobenzofuran that help define the key processes occurring. The initial step is phenyl-ether bond hydrogenolysis; however, this is followed by aromatic ring hydrogenation.  The complete catalytic disassembly of the more complex organosolv lignin to monomeric units, largely propyl-cyclohexanol derivatives is then described. Operational indices based on 1H NMR analysis are also presented that facilitate holistic evaluation of these product streams that within several hours consist largely of propyl-cyclohexanol derivatives. Lastly, we describe the application of this methodology with several types of wood (pine sawdust, etc.) and with cellulose fibers. The product distribution, albeit still complex, displays unprecedented selectivity towards the production of aliphatic alcohols and methylated derivatives thereof. These observations clearly indicate that the Cu-doped solid metal oxide catalyst combined with sc-MeOH is capable of breaking down the complex biomass derived substrates to markedly deoxygenated monomeric units with increased hydrogen content. Possible implementations of this promising system on a larger scale are discussed. 


One-pot Reduction of 5-hydroxymethylfurfural via Hydrogen Transfer from Supercritical Methanol

2. May 2012

Hansen TS, Barta K, Anastas PT, Ford PC, & Riisager A. Green Chemistry. 201214, 2457-2461.

DOI: 10.1039/C2GC35667H

AbstractReduction of 5-hydroxymethylfurfural

Catalytic conversion of HMF to valuable chemicals was achieved over a Cu-doped porous metal oxide in supercritical methanol. The hydrotalcite catalyst precursor is prepared following simple synthetic procedures, using inexpensive and earth-abundant starting materials in aqueous solutions. The hydrogen equivalents needed for the reductive deoxygenation of HMF originate from the solvent itself upon its reformingDimethylfurandimethyltetrahydrofuran and 2-hexanolwere obtained in good yields. At milder reaction temperatures, a combined yield (DMF + DMTHF) of 58% was achieved. Notably, the formation of higher boiling side products and undesired char from HMF is not detected under these reaction conditions.


One-pot Catalytic Conversion of Cellulose and of Woody Biomass Solids to Liquid Fuels

1. Aug 2011

Maton TD, Barta K, Iretskii AV, & Ford PC. J. Am. Chem. Soc. 2011133, 14090-14097. 

DOI: 10.1021/ja205436c

Catalytic conversion of cellulose and woody biomass to liquid fuelsAbstract

Efficient methodologies for converting biomass solids to liquid fuels have the potential to reduce dependence on imported petroleum while easing the atmospheric carbon dioxide burden. Here, we report quantitative catalytic conversions of wood and cellulosic solids to liquid and gaseous products in a single stage reactor operating at 300–320 °C and 160–220 bar. Little or no char is formed during this process. The reaction medium is supercritical methanol (sc-MeOH) and the catalyst, a copper-doped porous metal oxide, is composed of earth-abundant materials. The major liquid product is a mixture of C2–Caliphatic alcohols and methylated derivatives thereof that are, in principle, suitable for applications as liquid fuels.


 

Biomass and sustainable chemistry presentations since 2014

Invited talk: C. Bernt, "Understanding and enhancing th eselectivity of reductive lignin disassembly over doped porous metal oxides"

Christopher M. Bernt, Giovanni Bottari, Jacob Barrett, Megan Chui, Katalin Barta, Susannah L. Scott, Peter C. Ford

250th ACS National Meeting, Boston, MA, August 2015. 

Invited talk: P. C. Ford, “Upgrading Porous Metal Oxide Catalysts for the Reductive Disassembly of Lignocellulose to Value Added Platform Chemicals”  

Peter C. Ford, Christopher M. Bernt, Megan Chui, Zachary Jones, Giovanni Bottari, Felix Brunner, Hussaya Maneesuwan, Katalin Barta, Alexei Iretski, Susannah L. Scott

249th ACS National Meeting, Novel Catalytic Materials for Renewable Fuels/Chemicals. Denver CO, March 2015

Invited talk: P. C. Ford, “Studies of the reductive disassembly of lignin and lignocellulose using  Earth-abundant catalysts”

Peter C. Ford, Katalin Barta, Alexei V. Iretskii, Susannah L. Scott

248th ACS National Meeting, Catalysis Division Symposium: Catalysis for Biomass Conversion. San Francisco CA, August 2014

Invited talk: P. C. Ford, “Reductive disassembly of lignin and lignocellulose using Earth-abundant catalysts”

Peter C. Ford, Katalin Barta, Alexei V. Iretskii, Susannah L. Scott

18th Annual Green Chemistry & Engineering Conference of the ACS, Bethesda MD. June 2014

Contributed Talk: Z. Jones, “Supported metal catalysts for lignin hydrogenolysis”

Zachary Jones, Jessica Wu, Chris Bernt, Bryan Goldsmith, Susannah Scott, Baron Peters, Peter Ford

Symposium on Novel Catalytic Materials for Renewable Fuels/Chemicals, 249th ACS National Meeting, Denver 

Contributed Talk: Z. Jones, “Reactions of Lignin Model Compounds over a Hydrotalcite-Derived Copper Catalyst”

Zachary Jones, Jessica Wu, Chris Bernt, Bryan Goldsmith, Susannah Scott, Baron Peters, Peter C. Ford

Symposium on Catalytic Processing of Fossil and Biorenewable Feedstocks, AIChE Annual Meeting, Atlanta GA, 11/19/14

Contributed Talk: A. E. Leak, “The Role of Research Centers in Graduate Students’ Professional Development”

Anne E. Leak, Jason Tillman, Christopher Bernt, Clifford Kubiak, Lubella A. Lenaburg, and Peter C. Ford.

248th ACS National Meeting, Div. Chem Ed. Symp., San Francisco CA, August 2014

Poster: Megan Chui, Breanna Johnson, Christopher M. Bernt, Peter C. Ford, Petra Van Koppen, Darby L. Feldwinn, “Partnership for elementary school outreach: Developing an inquiry-based module to investigate CO2 production, consumption and levels of CO2 in the environment"

248th ACS National Meeting, Div. Chem Ed., San Francisco CA, August 2014

Poster: Zachary Jones, Chris Bernt, Giovanni Bottari, Hussaya Maneesuwan, Susannah Scott,  Peter Ford,  Katalin Barta, “Probing the Mechanism and Structure of a Lignin Reducing Cu Doped Porous Metal Oxide Catalyst” 

248th ACS National Meeting, Div. Inorg. Chem. San Francisco CA, August 2014

Poster: Megan Chui, Danielle Hamann, Anthony T. Tran, Felix M. Brunner, Alexei V. Iretskii, Mauricio Boscolo, Susannah L. Scott, Peter C. Ford, “Tuning the reductive disassembly of lignocellulosic biomass and model compounds using doped porous metal oxides"

248th ACS National Meeting, Div. Inorg. Chem., San Francisco, August 2014


 

Photochemistry and Small Molecule Bioregulator Presentations since 2014

Invited talk: P.C. Ford, PacificChem, Honolulu, Hawaii December 2015 

Invited talk: P.C. Ford, "Strategies for the photochemical uncaging of bioactive small molecules" 

10th International Conference on Pharmaceutical Science. Ribeirao Preto, Brazil. September 2015. 

Contributed talk: A.W. DeMartino, "Progress towards controlled biological release of CS2, a likely small molecule bioregulator"

Southern California Inorganic Photochemistry (SCIP) Conference, September 12, 2015. 

Contributed talk: P. Huang, "Cell-mediated delivery for Photo-activated NO Releasing Moieties" 

Southern California Inorganic Photochemistry (SCIP) Conference, September 12, 2015. 

Contributed talk: Z. Li, "Rhenium-manganese dinuclear metal carbonyl complexes as interesting photoCORMs" 

Southern California Inorganic Photochemistry (SCIP) Conference, September 12, 2015. 

Invited talk: P.C. Ford, "Nanoparticle strategies for photochemical delivery of bioactive small molecules"

Gordon Research Conference on Photochemistry, Easton, MA, July 2015. 

Invited talk: P.C. Ford, "Nanoparticle strategies for photochemical delivery of bioactive small molecules"

Aregentina National Meeting on Physical and Inorganic Chemistry (aaiFQ). Buenos Aires, April 2015. 

Invited talk: P.C. Ford, "Strategies for the photochemical uncaging of bioactive small moleclules"

249th ACS National Meeting, Denver, CO, March 2015

Contributed talk: A.W. DeMartino, "Carbon disulfide: a potential small molecule bioregulator." 

Southern California Inorganic Photochemistry (SCIP) Conference, September 27, 2014. 

Invited talk: P.C. Ford, "Mechanistic studies of NO and NOx reactions with heme and non-heme iron"

248th ACS National Meeting, San Francisco, CA, August 2014

Poster: Anthony W. DeMartino, Elizabeth S. Levy, Peter C. Ford, "Mechanistic insights and new systems based on 1,1-dithiooxalate, a photochemical precursor to carbon disulfide, a small molecule with biological potential"

248th ACS National Meeting, San Francisco, CA, August 2014

Poster: Meredith A. Crisalli, Lilian P. Franco, Agustin E. Pierri, Po-Ju Huang, Roberto S. da Silva, Peter C. Ford, "Release of nitric oxide from ruthenium centered photoNORMs an their use as small molecule delivery platforms"

248th ACS National Meeting, San Francisco, CA, August 2014